Research And Implementation Of Embedded Graphical Middleware

The application of embedded system gets a rapid development in recent years.Now the research on embedded technology has been a hot topic.With the expanding of market demands and the declining of hardware cost, more and more embedded system begins to provide graphical user interface for user's operation.Embedded developers are like to use a mature embedded graphical middleware to shorten development time and improve the efficiency of UI (user interface).This paper has compared several relatively mature embedded grahpical middlewares , analysised the overall structure and sub-layers' function of the middlewares, deeply studied the message mechanism,clip region principle,window's structure and management etc.In the later chapers of the paper,the implement of a new embedded grahical middleware—EplGUI is described.Traditional embedded graphical middleware is usually a simplified version of PC GUI. This paper analyzes disadvantages of the structure of the middleware when it is used on embedded device of low resource , makes a better combination of message mechanism and object-oriented technology , proposes a new middleware structure and applies it to EplGUI.The controls of a main window will not limited to a fixed and big control structure.The middleware structure will not affect the windows' efficiency and use few memory . EplGUI allows a sub window to define its own message routing function to improve the message dispatching speed if the controls in the window were arranged in a regular order.To show a irregular shape window,this paper used and improved Leonov's polygonal boolean operation algorithm and fixed the bug of redundant borders when it applied to polygonal window's clip region.The improved algorithm can be used in high performance embedded device to implement window of complex shape.To solve the problem of too large amout of rectangle clip region's calculation cost and memory used,this paper presents a clip region switching algorithm which has a lower average time and space complexity.The algorithm is simple and banausic.It can improve the switching speed of active windows and use low system resource.Finally this paper detailed describes the implementation of various controls in EplGUI .A simple control can only deal with a few messages and need not to have a big window structure.A complex control can be created by the expansion of existing controls using object-oriented technology. For the listbox which is mostly used in embedded system,a listbox data processing abstract level is proposed in this paper which can reduce the memory fragments and improve the stability of system.